The invention relates to an electromagnetically operable valve having a valve stem and a valve body. Preferred embodiments of the invention relate to an electromagnetically operable valve with a valve seat and a valve body, a valve stem, which forms a guide part provided with a shoulder, by way of which guide part the valve is axially movably guided in a valve guide, a valve disk which, in the closing position of the valve, while forming an hydraulically effective seat diameter, rests against the valve seat, an electromagnetic adjusting device and a spring by which the valve can be guided into end positions, and a control space with a fuel pressure bore formed between a shoulder of the guide part and the valve disk, hydraulic forces in the control space acting upon the shoulder and the valve disk.
A valve of the above-mentioned type of an injection arrangement is known from German Patent Document DE 34 06 198 C2. The electromagnetically operable valve has a valve seat, a valve stem with a guide part, a valve disk, an electromagnetic adjusting device and a spring. By way of the guide part, the valve is axially movably guided in the valve guide. The adjusting device and the spring guide the valve into the end positions. In the closing position of the valve, the valve disk rests against the valve seat. The guide part has a shoulder which forms a control space with a fuel pressure bore between itself and the valve disk. In the control space, hydraulic forces act upon the shoulder and the valve disk.
It is a disadvantage of the above-mentioned valve that, during the operating time of the valve, the hydraulic conditions in the control space change toward an imbalance. During its operating time, the valve disk will work itself into the valve seat which considerably increases the hydraulically effective seat diameter of the valve and thus the hydraulic force acting upon the valve disk and causes an earlier opening of the valve or, in extreme cases, an unintentional opening of the valve already during the injection.
Concerning the general technical background, reference is also made to German Patent Document DE 30 06 576 C2.
It is an object of the invention to construct a valve such that an optimal closing and opening operation of the valve is ensured during its whole operating time.
This object is achieved in certain preferred embodiments of the invention by providing an arrangement of the above noted type wherein the hydraulically effective seat diameter of the valve is limited such that the hydraulic forces acting upon the shoulder of the guide part and the valve disk in the closing position of the valve are essentially balanced.
An important advantage of the invention is the fact that, as the result of limiting the hydraulically effective seat diameter, the hydraulic forces in the control space are essentially balanced and the magnetic force of the adjusting device which is responsible for the closing position of the valve can therefore be designed to be lower. An unintentional opening of the valve in the closing phase is effectively prevented. The abrasive wear on the valve seat caused by particles which are transported by the fuel has only negligible effects on the closing and opening function of the valve. Even during a long operating time of the valve, the hydraulic conditions in the control space stay approximately the same.